The present invention generally relates to magnetic information storage devices and more particularly to a fabrication process of an integral thin-film magnetic head for use in a compact magnetic information storage device that records and reproduces information signals on and from a rigid magnetic disk that is revolved at a high speed in a hermetically sealed environment.
In the magnetic information storage devices of the so-called hard disk, a rigid magnetic disk revolving at a high speed such as several thousand r.p.m. is used for a recording medium, and recording and reproduction of information signals are achieved on and from the magnetic disk by means of a magnetic head that scans the surface of the magnetic disk without establishing contact therewith. The conventional hard disk device having a construction as such generally provides a very high access speed in the order of ten milliseconds or less and is used extensively as the auxiliary storage devices of computers and microprocessors. On the other hand, the conventional hard disk device occupies a considerable space mainly due to the size of the floating magnetic head and the space in which the magnetic head moves, and there exists a substantial difficulty in the reduction in the size of the device. Further, such a conventional hard disk device that uses a floating magnetic head is vulnerable to external shock.
On the other hand, there is proposed a new type of hard disk device that uses a very small, needle-like magnetic head that contacts with the surface of the revolving magnetic disk as shown in FIG. 1.
Referring to FIG. 1, the hard disk device is constructed on a base body 10 that defines a hermetically sealed space therein together with another base body part not illustrated. In the hermetically sealed space formed as such, there is provided a chassis 11 on which a shaft 12 is fixed. Further, the chassis 11 carries thereon a motor not illustrated in FIG. 1 and the motor drives a stage 13a such that the stage 13a revolves about the shaft 12 at a high speed typically in the order of several thousand r.p.m.
The stage 13a thus driven by the motor carries thereon one or more magnetic disks 13 wherein the magnetic disk 13 is formed of a rigid material such as aluminum and carries a magnetic coating. Further, a magnetic head assembly 14 is provided on the base body 10, wherein the magnetic head assembly 14 includes a shaft 16 that is fixed on the base body 10, and an arm 15 is mounted on the shaft 16 such that the arm 15 swings freely about the shaft 16. The arm 15 carries at a free end thereof a needle-like magnetic head member 17 that is urged to establish a continuous contact to the surface of the disk 13, typically with an urging force of about 1 mg. Further, the arm 15 is driven by an electromagnetic actuator 18 provided on the base body 10, and the needle-like magnetic head member 17 at the free end of the arm 15 scans the surface of the magnetic disk 13 in a radial direction thereof in response to the swinging motion of the arm 15.
It should be noted that the magnetic head member 17 carries a magnetic head at a tip end thereof, and the information signal picked up at the magnetic head part is transferred to a terminal pad 20 on the base body 10 via a flexible cable 19. Further, the flexible cable is used for supplying an electric power for actuating the arm 15. When recording information, on the other hand, the information signal is supplied to the magnetic head part from the terminal pad 20 via the flexible cable 19 for causing a magnetization of the magnetic disk 13 in response to the information signal.
FIG. 2 shows the arm 15 and the magnetic head member 17 attached thereto in more detail, wherein the arm 15 is formed of a resilient material such as aluminum and the magnetic head member 17 is attached to the arm 15 by an adhesive. Further, it will be noted that the arm 15 is formed with a U-shaped part in correspondence to a part that is mounted on the magnetic head assembly 14.
FIG. 3 shows the arm 15 and the head member 17 of FIG. 2 in the assembled state, wherein the arm 15 is mounted on a rotary sleeve 14a that in turn is fitted upon the shaft 16 shown in FIG. 1 such that the sleeve 14a can rotate freely about the shaft 16. The sleeve 14a carries a frame 14b that in turn carries a coil thereon, and the coil on the frame 14b is driven, with respect to a stator in the electromagnetic actuator 18, in response to a drive current that is supplied via the flexible flat cable 19. Thereby, the arm 15 experiences a swinging motion in response to the energization of the actuator 18.
FIG. 4 shows the cross sectional view of the hard disk device of FIG. 1, wherein only essential parts will be described.
Referring to FIG. 4, it will be noted that the base body 10 carries a motor M such that the motor M surrounds the shaft 12, and a rotor 13a is provided to surround the motor M. There, the rotor 13a is held rotatable about the shaft 12 by a bearing 13b and is driven upon energization of the motor M. The magnetic disk 13 is fixed upon the rotor 13a and revolves unitarily with the rotor 13a about the shaft 12. In the illustrated example, two magnetic disks are provided parallel about the common shaft 12. Further, it will be understood that the sleeve 14a is held rotatable about the shaft 16 by a bearing 14c. The electromagnetic actuator 18 includes stator magnets that are disposed above and below the frame 14b.
In FIG. 4, it is important to note that the needle-like magnetic head member 17 establishes a contact engagement with the surface of the magnetic disk 13. As already mentioned, the arm 15 resiliently urges the head member 17 upon the magnetic disk 13, and the recording and reproduction of information signals is achieved in the state that the head member 17 maintains the contact engagement with the surface of the revolving magnetic disk 13. By using the needle-like magnetic head member 17, one can reduce the space occupied by the magnetic head in the hard disk device, and the number of the magnetic disks that are mounted on the common shaft can be increased. Alternatively, one can reduce the height of the hard disk device.
FIG. 5 shows another conventional example of the magnetic head assembly used in the hard disk device of the foregoing type, wherein the magnetic head assembly is designated by a numeral 24 and includes a swing arm 25 adapted to be mounted on the rotary sleeve 14a at a circular cutout 25a and has flat upper and lower major surfaces extending straight in the radial direction of the arm 25. There, the arm 25 carries on either of the upper major surface or lower major surface an intermediate member 25 in correspondence to the free end of the arm 25, and the intermediate member 25 is formed with a mount surface 27a at a distal end thereof for carrying the integral thin film magnetic head body 17.
FIG. 6 shows the side view of the magnetic head assembly 24, wherein it will be noted that the mount surface 27a is formed to extend obliquely and the magnetic head body 17 carried thereon establishes a contact engagement with the magnetic disk 13 with an optimized contact angle. Typically, the magnetic head body 17 is attached to the surface 27a by an adhesive or welding. Further, the intermediate member 27 is provided at the free end of the arm 25 by a slider part 27b that engages with a guide groove 27c formed at the free end part of the arm 25 for minute adjustment. After the slider part 27b is adjusted with respect to the proper contact angle, the member 27 is fixed upon the arm 25 by an adhesive such as epoxy or by welding.
FIG. 7 shows the integral magnetic head member 17 in an enlarged scale.
Referring to FIG. 7, it will be noted that the magnetic head member 17 includes an integral head body 17a that carries a magnetic head at a head portion 17b that in turn is defined in correspondence to the tip end of the head body 17a, while the root end part of the body 17a located at the opposite side is adapted for mounting on the mount surface 27a of the member 27. The head portion 17b includes therein a thin film magnetic head of which construction is shown in the enlarged cross sectional view of FIG. 8.
Referring to FIG. 8, the head portion 17b includes a magnetic yoke 17.sub.1 embedded in aluminum oxide that forms the integral magnetic head body 17a, wherein the magnetic yoke 17.sub.1 includes an upper yoke 17.sub.2 and a lower yoke 17.sub.3, and a main yoke 17.sub.4 is formed at the front end part of the head portion 17b in continuation with the upper yoke 17.sub.2. Thereby, a gap 17.sub.5 is formed between the yoke 17.sub.4 and the yoke 17.sub.3, and a coil 17.sub.6 is wound around the upper yoke 17.sub.2. Further, in correspondence to the gap 17.sub.5, the magnetic head body is formed with a contact surface 17.sub.7 for establishing a contact with the surface of the magnetic disk, and the magnetic flux penetrates into the magnetic coating on the disk 13 in correspondence to the gap 17.sub.5. Further, a conductor strip 17.sub.9 extends from the coil 17.sub.6 along the body 17a to a terminal pad 17.sub.8 that is provided at the root part of the magnetic head body 17a.
FIG. 9 shows the magnetic head body 17 of FIG. 8 in a plan view.
Referring to FIG. 9, it can be seen that the magnetic yoke 17.sub.2 extends in the longitudinal direction of the head body 17 and the coil 17.sub.6 is wound around the yoke 17.sub.2. Further, respective ends of the coil 17.sub.6 are connected to lead conductors 17.sub.9a, 17.sub.9b that in turn are connected to terminal pads 17.sub.8a and 17.sub.8b respectively, wherein the lead conductors 17.sub.9a, 17.sub.9b correspond to the lead conductor 17.sub.9 while the terminal pads 17.sub.8a and 17.sub.8b correspond to the terminal pad 17.sub.8.
The fabrication process for fabricating the integral thin film magnetic head of FIG. 9 is disclosed in the U.S. Pat. No. 5,041,932 to Hamilton, op cit., and FIG. 10 shows the fabrication process of Hamilton. In the fabrication process, a number of the integral thin film magnetic heads are formed simultaneously on a substrate by repetitive deposition processes, and the magnetic heads thus formed are separated from each other by dissolving a separation region that defines individual magnetic heads by an etching process.
Referring to FIG. 10, the integral thin film magnetic head 17 is constructed on a silicon substrate 31 that has a principal surface on which an adhesion layer 32 of Ti and an electro-plating base 33 of a conductive material such as Cu are deposited successively for example by a sputtering process.
On the electro-plating base 33, a Cu layer 34 is deposited by an electro-plating process with a thickness of 5-25 .mu.m, and a photoresist (not shown) is applied on the layer 34 thus formed after smoothing the surface thereof. The photoresist is patterned subsequently to form a mask pattern that exposes selectively the surface of the layer 34 in correspondence to the separation region mentioned previously, and a copper stripe 37a is grown thereon by an electro-plating process. As will be described later with reference to FIG. 11, the separation region extends straight and surrounds each elongated magnetic head 11 laterally.
Next, the mask is removed and a new mask is formed to expose selectively the surface of the layer 64 in correspondence to the region wherein the terminal pads 17.sub.8a, 17.sub.8b are to be formed, and a gold layer is deposited on the layer 64 in correspondence to the exposed surface thus formed with a thickness of 6-10 .mu.m to form the foregoing pads 17.sub.8a and 17.sub.8b. Next, the mask is removed and an adhesion layer 35 of Ti is grown on the entire surface of the structure followed by a deposition of Al.sub.2 O.sub.3 to form a layer 36 by a sputtering process, wherein the layer 36 is grown with a thickness of 6-10 .mu.m. Further, the resulting surface is lapped and polished until the copper strip 37a and the terminal pads 17.sub.8a, 17.sub.8b are exposed.
On the planarized surface thus formed, a Ti adhesion layer 38 and a Cu electro-plating base 39 are deposited consecutively similarly to the previous process for forming the layers 32 and 33, and a mask (not shown) is formed thereon by depositing a photoresist and patterning the same subsequently. Further, by using the mask, a bottom part pattern 17.sub.5a forming the bottom pattern of the coil 17.sub.6 as well as the lead conductor patterns 17.sub.9a, 17.sub.9b are formed on the electro-plating base 39 by conducting an electroplating of Cu. Thereby, not only the Cu layers 17.sub.9a, 17.sub.9b and 17.sub.6a are formed as already mentioned but also a Cu layer 37b is formed on the base 39 in correspondence to the Cu stripe 37a. Thereby, the layer 37b increases the height of the Cu stripe 37. Further, the mask is removed and replaced by another mask that selectively exposes the surface of the Cu layer 37b as well as a part of the layer 17.sub.6a on which a vertically extending pattern of the coil 17.sub.6 is to be formed, and an electro-plating of Cu is conducted to deposit a Cu layer simultaneously on the strip 37b and on the bottom pattern 17.sub.6a to form a Cu strip 37c and a vertically extending pattern 17.sub.6b of the coil 17.sub.6 as illustrated. Further, the mask is removed and Al.sub.2 O.sub.3 is deposited to fill the depression formed on the structure as a result of the growth of the Cu strip 37c and the vertical coil pattern 17.sub.6b.
After the foregoing process, the surface of the structure thus obtained is lapped and polished to form a planarized surface, and a mask is formed to expose selectively the strip 37c, the pattern 17.sub.6b and in addition a region on which the upper yoke 17.sub.2 is to be formed. Further, a Ti adhesion layer and an electro-plating base are deposited consecutively thereon similarly to before on the exposed surface, and an electro-plating deposition of Cu is conducted on the electro-plating base thus formed to form a strip pattern 37d of Cu as well as the upper yoke 17.sub.2. Further, a Cu pattern 17.sub.6c is grown at both sides of the yoke 17.sub.2 simultaneously. Next, the mask is removed and replaced such that the yoke 17.sub.2 thus formed is covered, and the electro-plating of Cu is continued to form a strip pattern 37e on the strip pattern 37d and to form a vertical pattern 17.sub.6d in continuation to the vertical pattern 17.sub.dc of the coil 17.sub.6. Further, the mask is removed and the depression formed in the structure as a result of the growth of the Cu patterns above is filled by Al.sub.2 O.sub.3.
Next, the structure thus formed is lapped and polished to form a planarized upper major surface, and a mask is provided to expose selectively the Cu strip pattern 37e and a region on which the lower pattern of the coil 17.sub.6 is to be formed. Further, the Ti adhesive layer and the Cu electro-plating base are deposited similarly as before, and an electro-plating of Cu is conducted to form a strip pattern 37f and pattern 17.sub.6e that corresponds to the lower pattern of the coil 17.sub.6. Further, the mask is replaced by a new mask that exposes selectively the layer 37f thus formed and in addition the part of the layer 17.sub.6e on which the bridging part of the yoke shown in FIG. 8 (the part bridging between the upper yoke 17.sub.2 and the lower yoke 17.sub.3) is to be formed, and an electro-plating process is conducted to form a Cu strip pattern 37g as well as the bridging part not illustrated in FIG. 10. After this, the mask is removed and the depression formed thereby is filled by Al.sub.2 O.sub.3.
Next, the upper major surface of the structure thus formed is lapped and polished to form a planarized surface until the bridging part formed in the previous step and the strip pattern 37g are exposed, and a Ti adhesion layer and a Cu electro-plating base are deposited consecutively on the exposed surface of the strip pattern 37g as well as on a region on which the lower yoke 17.sub.3 is to be formed. Further, an electro-plating of Cu is conducted to form the lower yoke 17.sub.3 as well as a strip pattern 37h. After this, the mask is replaced such that the pattern 17.sub.3 is protected, and the electro-plating deposition of Cu is continued until a strip pattern 37i is grown while using a patterned resist as a mask. Further, the mask is removed and the depression formed as a result is filled by Al.sub.2 O.sub.3, and the structure thus formed is subjected to an finishing process wherein the upper major surface of the structure is lapped and polished to have a planar surface. Finally, a deposition of Al.sub.2 O.sub.3 is made in correspondence to the tip end of the head portion 17b, although not illustrated in FIG. 9.
FIG. 11 shows the structure thus obtained in a plan view, wherein a number of the elongated thin film integral magnetic heads are formed on the common substrate or wafer 31 in a parallel and mutually contacting relationship. There, it should be noted that the each elongated magnetic head 17 is laterally surrounded or defined by a Cu strip 37 that in turn is formed of the Cu strips 37a-37i stacked as already explained. There, the substrate 31 is scribe-cut into one or more plates 170 each including a number of the magnetic heads 17 aligned in one direction, and a deposition of the main yoke 17.sub.4 is conducted upon the side edge of the plate 170 in correspondence to individual end surfaces of the magnetic head 17.
The plate thus processed is then subjected to an etching process wherein the plate is immersed in an etching bath that contains an etchant such as a mixture of H.sub.2 SO.sub.4 and H.sub.2 O.sub.2. There, the Cu strip 37 in the scribe-cut plate is selectively dissolved by the etchant, wherein the etchant acts further upon the Cu layer 34 at the interface between the substrate 31 and the magnetic head 17. Thereby, the magnetic heads 17 are separated from each other, and each magnetic head 17 is recovered and mounted on the arm 15 shown in FIG. 2 or on the surface 27a of the member 27 shown in FIG. 5.
In the foregoing fabrication process of the magnetic head 17, it will be easily noted that one needs to have a substantial skill for assembling the magnetic head upon the arm to form a magnetic head assembly. More specifically, one has to pick up the individual needle-like magnetic head and mount same upon the suitable arm such as the surface 27a of the member 27. It should be noted that each magnetic head 17 typically has a width of 0.5 mm, a height of 0.05 mm and a length of 8 mm. In addition, the major part of the integral magnetic head is formed of brittle and fragile Al.sub.2 O.sub.3. Thus, the handling of the magnetic head has been extremely difficult.